|
Leaves: Site of photosynthesis and gas exchange
|
|
Stem: Contains vascular bundles which transport water/mineral salts as well as manufactured food respectively to different parts of the plant
|
|
Roots: Site of water/mineral salts absorption
|
|
Flowers: Contains reproductive organs of the plant
|
|
Plants are autotrophs: They make their own food by a process of photosynthesis
|
|
Raw materials: Carbon dioxide (diffuse in through stomata) and water (absorbed through roots)
|
|
Conditions: Chlorophyll pigment found in chloroplast traps light energy
|
|
Products: Glucose (used by plant) and Oxygen (released to surroundings)
|
|
Photosynthesis is a process in which green plants trap light energy and convert it to chemical energy for the formation of carbohydrates. This process involves the break down of inorganic molecules to synthesise inorganic molecules
|
|
This process starts of with light breaking down the water molecules into hydrogen and oxygen by a process called photolysis
|
|
The hydrogen produced by this is used to reduce carbon dioxide to form glucose
|
|
Oxygen produced by photolysis diffuses out of the stomata into the surroundings
|
|
Glucose is used by the plant n many ways. This is called the fate of glucose
|
|
The various ways glucose is used by the plant
|
|
Some glucose produced is converted to starch, a storage molecule, for future uses
|
|
Some glucose is metabolized by the plants (used by aerobic respiration to release energy)
|
|
Some glucose is converted to cellulose to enhance the rigidity of the cellulose cell walls of plant cells
|
|
Some glucose reacts with nitrate ions to form amino acids which condense to form essential proteins used by the plant
|
|
Some glucose is converted to sucrose for transport around the plant
|
|
Some glucose is converted to fats and oils for energy storage in seeds
|
|
Limiting factors are abiotic factors that limit the rate of photosynthesis when present in a short supply
|
|
Such factors exist as raw materials of photosynthesis not always being readily available
|
|
Limiting factors of photosynthesis include: Co2 concentration, light intensity, temperature of environment
|
|
Temperature changes results in variation of photosynthetic enzyme activity, light intensity changes results in variation of the amount of light energy available to the plant to convert to chemical energy, change in amount of carbon dioxide affects amount of glucose produced
|
|
Linear change (factor in the x axis is limiting photosynthesis), when the graph plateaus (some other factor is limiting)
|
|
As temperature increases, kinetic energy of enzyme and substrate molecules increases, greater frequency of collisions, high enzyme activity. Beyond optimum temperature, enzymes will denature and lose their specific active sites and enzyme activity will decrease
|
|
Concentration of carbon dioxide outside the leaf is greater than inside the leaf. Hence carbon dioxide diffuses from the surrounding into the leaf through the stomata during photosynthesis
|
|
Concentration of oxygen inside the leaf is greater than outside the leaf. Hence oxygen diffuses out of the leaf into surroundings during photosynthesis
|
|
Opposite during aerobic respiration
|
|
Gas exchange--> diffusion of gases in and out of leaf through stomata
|
|
Waxy cuticle: Prevents water from evaporating from the top of the leaf (Made of wax to allow light to penetrate through)
|
|
Upper epidermis: Contains a layer of thin and transparent cells to allow light to penetrate through and fall on the palisade mesophyll layer
|
|
Palisade mesophyll layer: Contains vertically arranged palisade mesophyll layers which are tightly packed with chloroplast, allowing maximum light to be absorbed, maximizing photosynthesis
|
|
Spongy mesophyll layer: Contains spongy mesophyll cells that have intercellular air spaces in between them
|
|
Lower epidermis: Contains guard cells and stomata
|
|
Guard cell: Become turgid/flaccid due to effects of osmosis, controls the size of stoma during day and night
|
|
Stomata: Small opening which is controlled by guard cells, where gases and water vapour diffuse through diffuse through
|
|
Palisade mesophyll layer, spongy mesophyll, lower epidermis (descending chloroplast concentration
|
|
Nuclei in pollen grain: Generative nucleus (divides into two) and pollen tube nucleus
|
|
Nuclei found in ovum: Female nucleus
|
|
Double fertilizations (one nucleus fuses to form zygote whereas the other fuses to form endosperm
|
|
Pollen grain transferred from anther to sticky stigma of the flower. The pollen grain germinates into a pollen tube which will grow down the style of the flower. Pollen tube nucleus guides the growth of the pollen tube and the enzymes secreted by he pollen tube held o breakdown tissues surrounding it for optimal penetration down the style. The generative nucleus divides to form 2 haploid nuclei. At the micropyle of the ovary, the tip of pollen absorbs sap and bursts releases both the male nuclei into the ovary. One male nucleus will fuse with the female nucleus to form a zygote and the other male nucleus will fuse with another female nuclei to form the endosperm (support embryonic growth)
|
|
Nuclei in pollen grain: Generative nucleus (divides into two) and pollen tube nucleus
|
|
Nuclei found in ovum: Female nucleus
|
|
Double fertilizations (one nucleus fuses to form zygote whereas the other fuses to form endosperm
|
|
Pollen grain transferred from anther to sticky stigma of the flower. The pollen grain germinates into a pollen tube which will grow down the style of the flower. Pollen tube nucleus guides the growth of the pollen tube and the enzymes secreted by he pollen tube held o breakdown tissues surrounding it for optimal penetration down the style. The generative nucleus divides to form 2 haploid nuclei. At the micropyle of the ovary, the tip of pollen absorbs sap and bursts releases both the male nuclei into the ovary. One male nucleus will fuse with the female nucleus to form a zygote and the other male nucleus will fuse with another female nuclei to form the endosperm (support embryonic growth)
|
|
Plants contains a vascular bundle in the stems. This vascular bundle contains xylem tissue, phloem tissue as well as cambium cells. The vascular bundle plays an integral role in transport of water and manufactured food throughout the plant
|
|
Xylem - Tissue that transports water and mineral salts absorbed by the roots to other plants of the plant. The xylem tissue is dead (contains no organelles to prevent obstruction to flow of water and mineral salts) and the walls of the xylem tissue are lignified to provide sufficient mechanical support to ensure that the tissue will not collapse. No cross walls present
|
|
Phloem - Tissue that transports manufactured food (sucrose) from leaves to sink organs down the pressure gradient. Phloem contains two types of cells, sieve tube cells as well as companion cells. As the name suggests a sieve tube cell is accompanied by a companion cell. The sieve tube cell has degenerative protoplasm/most of organelles are absent(except cytoplasm) to prevent obstruction to flow of manufactured food down the phloem. Companion cells contain many mitochondria which release a lot of energy to load sugars into the sieve tube cells by active transport. High perforated sieve plates/cross-walls are also present in the phloem tissue
|
|
Root pressure
|
Hydrostatic pressure generated by the roots to drive water and mineral ions absorbed the roots into the xylem tissue
|
|
Capillary action in the xylem tissue
|
Flow of water up the xylem vessels by the combined effects of cohesion forces between water molecules as well as adhesion forces between water molecules and the wall of the xylem tissue
|
|
Transpiration pull
|
Pulling force produced in the xylem that drives water and mineral ions up the xylem tissue as a results of water loss in the leaves due to transpiration (replace the water lost)
|
|
Humidity
|
↑ humidity, ↑ WV in surroundings, ↓ steep WV concentration gradient, ↓ rate of diffusion of water vapour, ↓ transpiration
|
|
Wind Speed
|
↑ wind speed, ↓ WV in surroundings, ↑ steep WV concentration gradient, ↑ rate of diffusion of water vapour, ↑ transpiration
|
|
Light intensity
|
↑ light intensity, ↑ size of stomata, ↑ more water vapour can escape, ↑ transpiration
|
|
Temperature
|
↑ temperature, ↑ water on surface of spongy mesophyll cells evaporate and move into intercellular air spaces, ↑ water vapour lost, ↑ transpiration
|
|
Glucose produced from photosynthesis is converted to sucrose to prevent mitochondria in leaf cells from using it to release energy through aerobic respiration
|
|
Sucrose is first loaded by companion cells into sieve tube cells by active transport. WP of phloem decreases below xylem and water from xylem move into phloem. Pressure in phloem at leaf increases and manufactured food and water move down the phloem from leaf to sink organ. At sink organ, sucrose is loaded out of sieve tube cells with the help of companion cells by active transport. WP of phloem increases more than xylem and water from phloem move into xylem
|
No comments yet.
Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
